Development of a prototype of a colourimetric temperature indicator for monitoring food quality

Temperature greatly affects the food quality and safety. Temperature control is an important condition during distribution and storage. An intelligent and biodegradable temperature indicator packaging material was developed based on a natural and heat-sensitive pigment (anthocyanin – ATH). Different concentrations of ATH were incorporated into chitosan matrix films (2.00%, w/w) that were applied as a surface coating on card paper, forming the chitosan card paper system (CH-Sys). The novelty of this work is an alternative packaging material that is biodegradable, simple manufacturing and indicates temperature variations in a specific range by irreversible visual colour changes. The CH-Sys changed irreversibly the colour from light violet to light yellow in response to different temperature exposition (40 °C until 70 °C), independently of luminosity (0 or 1000 lx). The results indicated that the CH-Sys has a great potential for use as a temperature indicator prototype in the specific temperature range studied in this work.     

结冷胶-沙蒿胶-蓝莓花青素可食性膜的制备及其性能分析

利用蓝莓花青素对pH值的指示作用制备智能包装膜,以期解决食品保鲜过程中新鲜度的检测难题。以结冷胶、沙蒿胶和蓝莓花青素为主要原料,采用流延法制备智能指示膜,研究膜的色差、机械性能、水溶性、水蒸气透过率以及微观结构等分析其性能。结果表明,红外扫描和电镜分析表明沙蒿胶与结冷胶及蓝莓花青素之间具有良好的相容性;沙蒿胶能够提高结冷胶/沙蒿胶-蓝莓花青素膜的厚度、膜的断裂延伸率、水蒸气透过率,降低膜的抗拉伸强度和水溶性;结冷胶/沙蒿胶复配比8∶2(质量比)时,花青素膜的断裂延伸率最大为47.36%,水蒸气透过率为7.643×10^-6 g·m/(d·Pa·m^2),抗拉强度22.08 MPa,复配比4∶6(质量比)的膜厚度达到0.079 mm;复合膜对pH值的指示作用显著,可作为pH指示膜。本研究为新型食品保鲜智能指示膜的应用提供理论基础。     

A novel intelligent film with high stability based on chitosan/sodium alginate and coffee peel anthocyanin for monitoring minced beef freshness

This study aimed to develop a novel pH-sensitive intelligent film for monitoring minced beef freshness based on chitosan/sodium alginate (CS–SA) and coffee peel anthocyanin (CPA). The different CPA content effects on the internal structure, physical properties and pH sensitivity of the CS–SA films were investigated. The results showed low contents of CPA (≤2%) could be evenly distributed within the CS–SA matrix with good compatibility. The addition of CPA significantly improved the physical properties and pH sensitivity of the CS–SA films. The CS–SA film containing 2% CPA (CS–SA–CPA2) showed the best tensile strength, water vapour barrier performance and most noticeable colour change. Moreover, this film exhibited good colour stability after 120 days. The CS–SA–CPA2 film changed colour from light yellow to brown to dark brown during minced beef storage, successfully indicating freshness. Therefore, the CS–SA–CPA2 film has the potential to be a pH-sensitive material for monitoring minced beef freshness.     

Modeling of potassium sorbate diffusion through chitosan films

The mechanism of potassium sorbate (K-sorbate) release from chitosan films was studied as a function of immersion time in aqueous solution. Fick's law was applied to calculate the diffusion coefficient and the power law defining the type of diffusion mechanism. The novelty in this study is the compound diffusion mechanisms comparison through chitosan film (CF) and chitosan emulsion film. Initially, the lipid was selected to obtain the emulsion films. The evaluation was based on the water vapor permeability (WVP). The lower WVP (32.45% less than chitosan film) was found using 0.5 g/100 g of palmitic acid for 2.0 g/100 g of chitosan. Then, active chitosan films (ACF) were obtained incorporating K-sorbate on CF at 0.1 and 0.5 g/100 g of K-sorbate. Also, active palmitic acid-chitosan films (APEF) were obtained, incorporating 0.1 g/100 g of K-sorbate. The mechanisms of K-sorbate diffusion through ACF and APEF were mainly non-Fickian. However, the K-sorbate diffusion coefficient did not reduced in lipid presence.     

Development of cellulose nanofibrils reinforced polyvinyl alcohol films incorporated with alizarin for intelligent food packaging

Visual pH-sensing films were fabricated using cellulose nanofibrils (CNF) reinforced polyvinyl alcohol (PVA) and alizarin. The relationships between the ratio of PVA: CNF hydrogel (2:1, 1:1, 1:2) and the physical properties and colour response efficiency of indicator films were investigated. Fourier transform infrared spectroscopy of films evidenced alizarin and CNF was properly incorporated by physical interaction. A new weak X-ray diffraction peak appeared at 2θ = 22.4°, which was affected by the incorporation of CNF. The increase in the CNF content induced enhancements of thermal stability, tensile strength, water contact angle and colour sensitivity of the indicator films. The colourimetric films had a higher sensitivity to discolouration when exposed to acidic vapours than alkaline vapours. The films presented a remarkable colour change varied from purple in alkaline condition to yellow in acidic condition. Therefore, this colourimetric film can be used as a volatile acid sensor for intelligent packaging.     

Effect of carp (Cyprinus carpio) oil incorporation on water vapour permeability,mechanical properties and transparency of chitosan films

The effect of carp oil incorporation on properties of chitosan films was evaluated. Chitosan and carp oil were obtained from shrimp wastes and viscera respectively. Tests were performed with different values of chitosan: oil ratios, agitation rates, homogenisation times and pH. The optimum conditions for stability of the film–forming dispersions were of 20,000 rpm at 10 min, and 10:1 ratio of chitosan:oil. The highest values of tensile strength and elongation percentage (%E) of films were obtained at pH 3.5. The addition of carp oil in the chitosan films (10:1 ratio) showed an increase in the resistance to diffusion of water vapour (1.7 g mm m^?2 day^?1 kPa^?1) in relation to pure chitosan films (4.1 g mm m^?2 day^?1 kPa^?1). However, pure chitosan films showed better mechanical properties (38 MPa and%E 18%) and transparency than films of chitosan:oil (20.4 MPa and 8.8%).     

Characterization of antioxidant chitosan film incorporated with Zataria multiflora Boiss essential oil and grape seed extract

Antioxidant chitosan based edible films were developed incorporated with Zataria multiflora Boiss essential oil (ZEO) (5 and 10 g/L) and grape seed extract (GSE) (10 g/L) alone and in combination. The physico-mechanical, wettability, swelling index, color, total phenol and antioxidant characteristics of the films were investigated. Films without any agents were used as control sample. All films, with the exception of 10 g/L GSE + 10 g/L ZEO film, exhibited lower strength and elongation values, and only the addition of 10 g/L ZEO to GSE film improved the water vapor transmission rate of chitosan films. Only GSE containing films had higher swelling index. The incorporation of GSE and ZEO into chitosan film increased the wettability of the surface, total phenol and antioxidant activity. Neat chitosan and ZEO incorporated films had a light yellowish color, whereas GSE + ZEO films were gray.     

Optimization of purification conditions of radish (Raphanus sativus L.) anthocyanin-rich extracts using chitosan

This study developed a chitosan-treatment procedure to remove impurities from radish anthocyanin extracts to promote their utilization as natural food colorants. Effects of purification conditions (independent variables) including pH (3.7, 4.0, and 4.3), chitosan concentration (1.5, 2.0, and 2.5 g/100 mL), and treatment duration (2, 2.5, and 3 h) on anthocyanin content, glucosinolate content, and clarity of radish anthocyanin-rich extracts (dependent variables) were investigated via a Box–Behnken experimental design. A set of preferred chitosan treatment conditions was determined to be 2.74 h at pH 3.92 with an initial chitosan concentration of 1.59 g/100 mL, according to the desirability function analyses. Under these purification conditions, glucosinolate reduction was ∼61%, clarity was enhanced from 45.5% to 86.9%, and anthocyanin retention was ∼95%. This chitosan-treatment procedure uses a biodegradable agent, and is safe, economic and efficient for solving the off-flavor and clarification problems of radish anthocyanin extracts. The procedure requires no special equipment and has potential to be scaled up for commercial production.     

Chitosan/whey protein film as active coating to extend Ricotta cheese shelf-life

Shelf-life extension of Ricotta cheese coated with a chitosan/whey protein edible film and stored under modified atmosphere at 4 °C was evaluated. The chitosan/whey protein film had 35% and 21% lower oxygen and carbon dioxide permeability, respectively, and about three times higher water vapor permeability than film prepared with chitosan alone. Over a 30-day storage period, no differences in the pH of control and coated Ricotta cheeses were observed. While the titratable acidity of the control increased linearly during the first two weeks and remained constant for the rest of the storage period, the corresponding values for coated Ricotta cheese did not change significantly during the first 21 days and reached the acidity level (0.34 ± 0.02 milliequivalent/100 g of analyzed sample) of the control only on day 30. The viable numbers of lactic acid bacteria and mesophilic and psychrotrophic microorganisms were significantly lower (p < 0.05) in the chitosan/whey protein coated cheese, compared to the control, at each storage time. Our findings suggest a potential utility of chitosan/whey protein coatings to extend fresh dairy product shelf-life.     

Physico-mechanical properties of chitosan films with carvacrol and grape seed extract

The physico-mechanical properties of 3 films composed by carvacrol, grape seed extract (GSE) and chitosan in different proportions were studied. The films, prepared by solvent casting technique with the following compositions of the casting solutions in carvacrol, GSE and chitosan: film-1: 9.6 ppm–684 ppm–1.25% w/v, film-2: 60 ppm–400 ppm–1.2% w/v and film-3: 90 ppm–160 ppm–1.24% w/v and were compared to a control (1.25% w/v chitosan) film. Mechanical, structural, barrier and colour properties of the films were evaluated. Film-3 presented the lowest water vapour and carbon dioxide permeabilities (WVP and CO₂P) and tensile strength (TS) values and the highest oxygen permeability (O₂P), whereas film-1 presented the highest water content and the lowest crystallinity, CO₂P, TS and luminosity. These results suggest that in the range studied, carvacrol and GSE affect the film structure and its mechanical properties due to hydrophilic (GSE) and hydrophobic (carvacrol) compounds. This work will help the development of edible films, based on physico-mechanical properties, contributing to food preservation and shelf-life extension.     

Active/smart carboxymethyl cellulose-polyvinyl alcohol composite films containing rose petal extract for fish packaging

In this study, a film was developed for packaging fish that not only enhanced its shelf life but also was visually receptive to its spoilage. Rose petal extract (RPE) having excellent bioactivity was used as the functional component in carboxymethyl cellulose-poly vinyl alcohol packaging film. Due to its high anthocyanin content, RPE could be used as a pH indicator, as its colour changed from bright red (pH 2) to yellow (pH 10). The developed film was used for packing Indian Mackerel and assessing its quality during chilled storage. Mackerel packed in neat film spoiled in 3 days while that in RPE containing films had shelf life of 12 days. Total bacterial count, pH, total volatile basic nitrogen and thiobarbituric acid reactive substance of fish in control were higher as compared to in RPE films. On spoilage RPE containing films showed visible colour response from red to green.     

Preparation and characterization of chitosan/halloysite nanotubes composite film with ethylene scavenging and gas resistance for active food packaging

In this study, the halloysite nanotubes (HNT) were incorporated into chitosan (CS) to prepare CS/HNT composite film by solution-casting method. Different HNT contents were studied in relation to the morphological, optical, mechanical, barrier and thermal properties of CS/HNT composite films. After incorporation of HNT, the CS/HNT composite films showed improvement in UV light shielding, barrier against water vapor and oxygen, mechanical strength and thermal stability as well as achievement of ethylene scavenging property. Especially, when 5 wt% HNT were added, more homogenous distribution of HNT in CS matrix was observed by SEM, resulting in 169.9% increase in tensile strength, 52.94% decline in oxygen permeability and 4.07 times enhancement in the ethylene scavenging capacity at 100 kPa pressure compared with pure CS film. Moreover, the obtained film with 5 wt% HNT effectively maintained the freshness of bananas and cherry tomatoes under ambient conditions. This study demonstrated that the CS/HNT composite films could be used as active food packaging material to extend the shelf-life of fresh fruits and vegetables.     

Combined effect of ozonated water and chitosan on the shelf-life of Pacific oyster (Crassostrea gigas)

Effects of ozonated water and chitosan treatment on the shelf-life extension of Pacific oysters (Crassostrea gigas) stored at 5 ± 1 °C were studied. Results indicated that ozonated water treatment reduced the total microbial load of fresh oysters by about 10-fold (from 3.2 × 10³ CFU/g to 1.8 × 10² CFU/g) before storage and the microbial flora was different with that of raw samples. The wide-spectrum antibacterial property of chitosan against bacteria isolated from oysters was confirmed, and chitosan concentration of 5.0 g/l was eventually determined for application in oyster preservation. Based on microbiological analysis, biochemical indices determination and sensory evaluation, shelf-lives of 8–9 days for control, 10–12 days for ozonated water treated samples, 14–15 days for chitosan treated samples and 20–21 days for samples with combined treatment were observed, indicating that ozonated water and chitosan have a great potential for oyster preservation.Industrial relevanceAs seafood, Pacific oysters have a short shelf-life. Improvements in the shelf-life of oysters can have an important economic impact by reducing losses and by allowing the products to reach distant and new markets.In this work, Shelf-life of oysters with combined treatment of ozonated water and chitosan doubled, which has great practical meaning, and the process could be fully adopted by the food industry.We also did some research about the changes in microbial flora after ozonated water treatment. This work could help in preservation of oysters when ozone or ozonated water concerned.We discovered Wide-spectrum antibacterial property of chitosan against the strains isolated from raw oysters. The potential for using chitosan as a natural preservative in oysters was approved.     

Development and characterisation of functional cocoa (Theobroma cacao L.)-based edible films

The aim of this study was to develop functional edible films containing cocoa (Theobroma cacao L.) powder extract using alginate, pectin and chitosan in combination with proteins (whey protein isolate, soya and hemp protein). The films were examined for their physico-chemical (dry matter content, colour, thickness), mechanical (elongation at break (EAB)), bioactive (the content of total polyphenols (TPC), flavan-3-ols (F3olC), antioxidant capacity (AC)) and sensory properties. The plain alginate film exhibited the highest EAB (29.1%). The highest TPC and F3olC were determined in plain alginate (29 mg GAE/g and 2.75 mg (+)-catechin/g) and pectin (29 mg GAE/g and 2.25 mg (+)-catechin/g) films. The addition of proteins resulted in prolonged release of polyphenols and enhanced functional properties; however, the formation of protein–polyphenol complexes caused slight alterations in the bioactive composition of the films. The obtained results indicate a high potential of the developed films as functional, biodegradable form of active food packaging.     

Influence of thermal process on structure and functional properties of emulsion-based edible films

Synthetic food packaging is classically used to prevent mass transfer of various small molecules (water, gases, flavour compounds or solutes) between a food and its surrounding medium. In the case of composite foods, the development of edible films and coatings, applied between the different phases of this food is rising up. The increase of such food products shelf-life is indeed related to the barrier efficiency of these edible packaging against small molecules transfers. This is especially true for water transfer between compartments of different water activities in the same food, that leads to important physico-chemical changes and therefore to food quality deterioration. Film-forming substances used for this study associated an iota-carrageenan hydrocolloid matrix, that ensures good mechanical properties, in which a high melting point fat was dispersed to enhance moisture barrier properties. After the film drying in standardised conditions of temperature (30 °C) and relative humidity (40%), the emulsified films containing various contents of fat (30%, 60% or 90% dry basis) were also submitted to heat treatment (100, 150, 200 °C) and for different durations (1, 2, 4, 8 min) corresponding to those classically encountered in baking processes. The aim was to tend to a bilayer film structure from a single film manufacturing. Size and repartition of fat globules in the carrageenan matrix was characterised by laser light granulometry and film microstructure was observed by ESEM. Barrier efficiency to water was evaluated from water vapour permeability measurements. Contrary to previous observations on film drying, neither fat globule size nor film water permeability was significantly modified by such heat treatment. Moreover, no phase separation was noticed by microscopic observations of the film cross section. Therefore, carrageenan matrix represents a very powerful material for its structural properties to a system and is a good candidate for application such as encapsulation of active substances incorporated in biopolymer coatings or films for food packaging applications.     

Development of sago (Metroxylon sagu)-based colorimetric indicator incorporated with butterfly pea (Clitoria ternatea) anthocyanin for intelligent food packaging

Innovation in colorimetric sensors to detect early signs of food spoilage is a growing interest in food safety and quality control. Currently available chemical dyes for sensor applications have concern because of their possible migration into food packaging and food in contact. In this study, a colorimetric indicator was developed using natural butterfly pea (Clitoria ternatea) anthocyanin with Sago (Metroxylon sagu) as polymeric film. The principle was based on pH shift due to chemical processes produced by microorganism causing anthocyanin color to change. The film was fabricated by solvent casting method and characterized by color change at different pH values, total water solubility, swelling rate, and morphological structure. Trials on chicken breast samples in various conditions exhibited that the film indicator responded well according to pH variation enabling a real-time monitoring due to spoilage. Thus, our natural pH indicator with visible color variation allows for simple, economic and safe monitoring of perishable foods.     

蓝莓花青素智能指示膜的制备及应用

以蓝莓花青素(BA)作为新鲜度指示剂,以玉米淀粉(CS)、羧甲基纤维素(CMC)为成膜基材,采用流延法制备智能指示膜.分析不同质量分数花青素对复合膜在机械性能、含水率、水蒸气透过率、热稳定性、红外光谱、表面微结构以及灵敏度等的影响.结果表明:当BA质量分数为3％时,指示膜的断裂伸长率最高,含水率与水蒸气透过率最低,且灵...     

Preparation and properties of rice starch–chitosan blend biodegradable film

Biodegradable blend films from rice starch–chitosan were developed by casting film-solution on leveled trays. The influence of the ratio of starch and chitosan (2:1, 1.5:1, 1:1, and 0.5:1) on the mechanical properties, water barrier properties, and miscibility of biodegradable blend films was investigated. The biodegradable blend film from rice starch–chitosan showed an increase in tensile strength (TS), water vapor permeability (WVP), lighter color and yellowness and a decreasing elongation at the break (E), and film solubility (FS) after incorporation of chitosan. The introduction of chitosan increased the crystalline peak structure of starch film; however, too high chitosan concentration yielded phase separation between starch and chitosan. The amino group band of the chitosan molecule in the FTIR spectrum shifted from 1541.15 cm⁻¹ in the chitosan film to 1621.96 cm⁻¹ in the biodegradable blend films. These results pointed out that there was a molecular miscibility between these two components. The properties of rice starch–chitosan biodegradable blend film and selected biopolymer and synthetic polymer films were compared; the results demonstrated that rice starch–chitosan biodegradable blend film had mechanical properties similar to the other chitosan films. However, the water vapor permeability of rice starch–chitosan biodegradable blend film was characterized by relatively lower water vapor permeability than chitosan films but higher than polyolefin.     

花青素与姜黄素在食品包装领域的应用

花青素和姜黄素对于活性包装至关重要,探讨其内在机理,可为花青素、姜黄素智能包装膜的相关研究提供理论参考。本文综述了花青素、姜黄素的结构和性质、提取方法、抗氧化活性、花青素和姜黄素在食品包装上的应用以及两种色素混合在食品包装上的应用。花青素和姜黄素由于其自身结构特点,在不同的pH下有不同的颜色,花青素作为颜色指示剂变色范围广,但性质不稳定,易受到外界因素影响。姜黄素稳定性高于花青素,但变色范围窄。此外,两者均具有很好的抗氧化活性,可作为颜色指示剂与抗氧化剂应用在食品包装中。花青素和姜黄素的变色特点、稳定性以及功能活性对食品新鲜度指示包装的性能具有显著的影响,将两种色素混合作为指示剂添加到食品包装中,有助于提高花青素的稳定性,从而获得更好的指示效果。     

Influence of α-tocopherol on physicochemical properties of chitosan-based films

Chitosan has been exploited as a material for the development of edible films, and additionally can be used as a carrier of functional compounds such as α-tocopherol. The aim of this work was to evaluate the effects of the incorporation of α-tocopherol in chitosan-based films. FTIR and thermal analyses were performed and showed that the incorporation of α-tocopherol affects the chemical structure of chitosan-based films with the establishment of new chemical bonds and the decrease of crystallinity. Results also showed that the increase of α-tocopherol concentration promotes a decrease of water content (from 12.6 to 11.4%) of the films. The addition of α-tocopherol to chitosan films leads to a significant reduction (p < 0.05) of tensile strength from 34.06 to 16.24 MPa, and elongation-at-break from 53.84 to 23.12%. Film opacity values (ranging from 4.74 to 7.83%) increased when α-tocopherol was incorporated into the film. Antioxidant capacity of chitosan-based films was evaluated and was enhanced when α-tocopherol was present in the film matrix. Results showed that α-tocopherol can be successfully added to the chitosan films enhancing the final quality and shelf-life extension of food products.